I’ve thrown that at a few over the years. Is color the absence of reflection, or the absence of absorption?
Those quantities are compliments in a reflecting material. Colored glass can be anti-reflection coated, in which case there is no reflection, or at least very little, but even if the antireflection coating were perfect, the stained glass would still be colored the same way it would be perceived without the AR coating. Color is what happens when some parts of the visible spectrum are treated differently than other parts are, in such a way that the R/G/B ratios become different as perceived by human eyes.